(a/k/a FORMER WINDOM LANDFILL)
WINDOM, COTTONWOOD COUNTY, MINNESOTA
This document summarizes potential public health concerns associated with a capped landfill and the public water supply in Windom Minnesota. It is based on a formal site evaluation prepared by the Minnesota Department of Health (MDH). A number of steps are necessary to do such an evaluation:
- Evaluating exposure: MDH scientists begin by reviewing available information about environmental conditions at the site. The first task is to find out how much contamination is present, where it's found on the site, and how people might be exposed to it. Usually, MDH does not collect its own environmental sampling data. We rely on information provided by the Minnesota Pollution Control Agency (MPCA), U.S. Environmental Protection Agency (EPA), and other government agencies, businesses, and the general public.
- Evaluating health effects: If there is evidence that people are being exposed--or could be exposed--to hazardous substances, MDH scientists will take steps to determine whether that exposure could be harmful to human health. The report focuses on public health--the health impact on the community as a whole--and is based on existing scientific information.
- Developing recommendations: In the evaluation report, MDH outlines its conclusions regarding any potential health threat posed by a site, and offers recommendations for reducing or eliminating human exposure to contaminants. The role of MDH in dealing with hazardous waste sites is primarily advisory. For that reason, the evaluation report will typically recommend actions to be taken by other agencies--including EPA and MPCA. However, if there is an immediate health threat, MDH will issue a public health advisory warning people of the danger, and will work to resolve the problem.
- Soliciting community input: The evaluation process is interactive and ongoing. MDH starts by soliciting and evaluating information from various government agencies, the organizations responsible for cleaning up the site, and the community surrounding the site. Any conclusions about the site are shared with the groups and organizations that provided the information. Once an evaluation report has been prepared, MDH seeks feedback from the public. If you have questions or comments about this report, we encourage you to contact us.
Please write to:
Community Relations Coordinator
Site Assessment and Consultation Unit
Minnesota Department of Health
121 East Seventh Place/Suite 220
St. Paul, MN 55164-0975
OR call us at: (612) 215-0916 or 1-800-657-3904 (toll free call--press "4" on your touch tone phone)
In 1989 the Minnesota Department of Health (MDH) prepared a Public Health Assessment on the Windom Landfill Site (Site) for the Agency for Toxic Substances and Disease Registry (ATSDR). Further Site Reviews and Updates (SRU) on the Site were prepared by MDH in 1993 and 1995. The Site is often referred to as either the Windom Dump Site or the Former Windom Municipal Landfill Site. This Health Consultation will briefly review information from previous MDH documents, discussions between the City of Windom (City), the Minnesota Pollution Control Agency (MPCA), and MDH concerning the need for increased water production from the municipal water system, review the 1996 - 97 Annual Evaluation Report (Wenck 1997b), and discuss monitoring data from City Wells not believed to be impacted by the Site. The background, history and previous investigations conducted at the Site have been discussed in detail in the 1989 Public Health Assessment (MDH 1989) and the 1993 SRU (MDH 1993).
The Site is in the City of Windom, Cottonwood County, Minnesota. The current population of Windom is 4555. The Site is listed on both the federal Superfund list and the Minnesota Permanent List of Priorities. The Site is an 11 acre former municipal landfill facility that operated from the 1930s through 1986 and is owned by the City of Windom. Wenck Associates, Inc. is a consultant for the City on the Site. Groundwater and soil at the Site is contaminated with volatile organic compounds (VOCs). Surface water is not believed to be impacted by the contamination on the Site. As a result of an investigation of soil and groundwater contamination associated with the Site in the 1980s, the Site was capped and a recovery well system and an outdoor spray treatment process were installed. The treatment facility became operational in October 1990. Figure 1 presents a map of the Site and the surrounding area depicting groundwater flow and capture zones created by the on-site recovery well system.
A 5-year review was completed by the MPCA for the Environmental Protection Agency (EPA) in February, 1995. It concluded that the groundwater extraction well system was functioning properly, and provided adequate protection of human health and the environment. It recommended that the City of Windom continue to operate the groundwater extraction system, spray nozzles, and roof vent in the municipal water treatment system, and that periodic sampling of the treated water entering the municipal system continue. It also recommended continued monitoring of city well #7 (CW7). CW7 is closer to the Site than any other municipal well and historically had the highest VOC contamination levels. When the pump and treat system was installed, CW7 was hooked to it as a pumpout well.
Meeting City Water Needs
The City of Windom is in need of wells to supplement water from its 5 active wells. Demand is projected to increase 150 percent over the next 20 years (Wenck 1996b). In August 1996, the City proposed using water from 2 recovery system pumpout wells (RWA and RWC) and the offline CW7 as municipal supply wells (Wenck 1996b).
CW7 was utilized as a recovery system pumpout well from 1990 until it was disconnected in August, 1994. The decision to disconnect CW7 from the recovery system (accomplished 8/94) was based on eight consecutive quarters of water quality which was below all action levels established in the Record of Decision (ROD) for the site. There have been no detects of VOCs in CW7 since, and the well is scheduled for reconnection to the municipal water system. In 1996, Windom received permission from MPCA to reconnect CW7 to the municipal water system. Given the history of vinyl chloride detection in CW7 and the increased usage of water in the unconfined aquifer, MDH has some concerns about reconnecting the well. But, given regular sampling of CW7, these concerns are limited.
Vinyl chloride and cis-1,2-dichloroethene have not been detected in RWC since July 1994. Detected concentrations of vinyl chloride at RWA have remained around the detection limit (0.3 to 1 g/l) since July 1994. Both RWA and RWC are within the site boundaries and are 2 of the 3 remaining pumpout wells.
In a letter to Wenck (MDH 1996) (attached), MDH recommended against the August 1996 proposal. This conditional recommendation was based on:
- the proximity of CW7, RWA and RWC to the landfill,
- the lack of data on the effects of pumping large quantities of water from the wells and not recharging the groundwater source with recycled water, and
- the potential to change groundwater flow in the area of the landfill.
Further recommendations to the City and their consultants included:
- a Wellhead Protection Plan be prepared by the City to address future water needs and potential problems which may be associated with proximal contamination sources,
- experiments be conducted to validate the proposed groundwater model, and
- that any use, or proposed use, of CW7 or any of the recovery wells as a municipal water supply be evaluated thoroughly prior to implementation.
The City of Windom decided in April 1997, as noted in a report filed by Wenck (Wenck 1997a), to reattach CW7 to the municipal system and to drill a new well at a location where impact from the Site is not expected. MDH believes that this is a reasonable decision if contamination in CW7 is monitored and remains below levels of concern.
1996-1997 Annual Evaluation Report
The 1996-1997 Annual Evaluation Report prepared by Wenck, Associates, Inc. (Wenck 1997b) contains a summary of the groundwater pumpage from the Recovery Well System, groundwater elevation data, a summary of water quality and organic detections, and a sampling plan for the 1997 - 1998 project year. The report, submitted to MPCA, depicts the Recovery Well System as effectively capturing groundwater flow beneath the landfill. Graphic results from the groundwater flow model developed in 1996 (Wenck 1996a) are shown in Figure 1. Modifications to the model, developed from new data as well as in response to communications from MDH and MPCA, have been incorporated (Wenck 1997a). The model represents the "worst case" scenario of the capture zone and indicates effective capture of groundwater flow beneath the entire Site. A large portion of the recycled water from the spray treatment sites remains in the recovery capture area. Monitoring results from MW11 should give a good indication of the quality of the uncaptured treated water, and have consistently shown no contamination of concern.
Volatile Organic Compounds
Groundwater monitoring at the Site indicates that five VOCs are present at detectable concentrations. Chlorination of the wells is routinely performed in Windom due to the presence of iron bacteria. Bromodichloromethane, chlorodibromomethane, and chloroform were detected in City Well 8 (CW8) and are likely due to well chlorination performed by the city (Wenck 1997b). Chloroform detections in CW7, MW1, and a single RWA duplicate during the October 1996 sampling are suspected to be the result of laboratory contamination (Wenck 1997b). Vinyl chloride, and cis-1,2-dichloroethene were detected in RWA, RWB, MW1 and MW5A and have been the primary detects associated with the landfill for years. Of these 2 contaminants, only vinyl chloride was above MDH Health Risk Limits (HRL; 0.2 g/l), with a maximum concentration of between 0.4 and 4 g/l (Attachment 1) for the reporting year of April 1996 to April 1997. A HRL is the concentration of a groundwater contaminant that can be safely consumed daily for a lifetime. The Maximum Contaminant Levels (MCL) for vinyl chloride is 2.0 g/l and this is the regulatory standard for public water supplies. MDH considers HRLs protective of human health, while MCLs are not always protective of human health.
Vinyl chloride concentrations above detection limits were found in fifteen samples from CW8 from 1992 to 1994, with a maximum of 0.4 g/l (all detects below statistical quantification limit but with peak present and quantified). Sampled water from CW8 has not had detectable concentrations of vinyl chloride in the 11 samples collected since July 1994 (through April 1997). The water from this well continues to be blended with the remaining wells in the municipal system and treated by aeration prior to delivery. CW7 is the only other city well from which vinyl chloride contaminated samples have been analyzed. CW7 (not connected to the city municipal system from 1990 to present) last recorded detectable concentrations of vinyl chloride in 1993. Levels of vinyl chloride in the general municipal system continue to remain below detection limits and do not pose a current health threat.
Since startup in 1990, the pumpout system has removed an estimated 40.7 pounds of contaminants, with approximately 1.2 pounds of volatile organics being removed during project year 1996 - 97 (Wenck 1997b). MDH remains concerned about the levels of vinyl chloride detected in monitoring and recovery wells at Windom. The appearance of vinyl chloride in MW1 in April 1995 and in all MW1 samples since that date is of particular concern. These detections demonstrate a change in the groundwater quality in these areas which should be evaluated.
It is not known whether vinyl chloride contamination at this site ever represented a public health hazard. Vinyl chloride was detected in CW#7 above MDH's current HRL when the well was removed from the water supply system. Water supply mixing may have kept delivered water below levels of concern. Furthermore, health risk from vinyl chloride may have been limited by the actual duration of exposure.
Nitrate, which has historically approached the MCL and HRL (10 mg/l) in monitoring wells at the Site, was below levels of concern for each of the monitoring events during the 1996 - 97 monitoring year (maximum - 0.38 mg/l). Data reviewed include data from all city, monitoring, and recovery wells.
Sampled inorganic water quality parameters were below levels of concern. Inorganic arsenic was also below detection limits (5 g/l) in all samples taken during the 1996-97 reporting year except in RWB where samples contained 7 g/l in April 1996 and 5 g/l in April 1997. The action level for arsenic at the site as stated in the ROD is 12.5 g/l.
MDH is generally concerned about levels of arsenic in drinking water. Western Minnesota is known to have higher levels of arsenic in groundwater than other regions of the state, and there is some historical data which shows elevated levels of arsenic in samples from wells in Windom. MDH has reviewed data from the municipal wells, monitoring wells, and recovery wells back to 1982 (Wenck 1997b). Out of 175 samples analyzed for arsenic and reviewed by MDH, 9 showed concentrations of greater than 10 g/l. The 9 samples are listed in the table below:
|Arsenic (As) concentrations greater than 10 g/l||Ratio of Samples w/ 10g/l As: total # of samples|
|July 11, 1983||MW2||SERCO||1000 g/l||yes||10/11|
|July 11, 1983||MW3||SERCO||2000 g/l||yes||4/5|
|February 24, 1986||MW6||MPCA/MDH||110 g/l||no||*|
|August 19, 1986||MW6||EAH||75||yes||*|
|June 24, 1987||MW6||EAH/ALR||69||no||*|
|August 11, 1987||MW6||EAH/ARL||56||yes||*|
|July 20, 1988||MW6||WAI/ARL||45||no||*|
|June 22, 1987||MW7A||EAH/ARL||24||no||3/4|
|June 24, 1987||MW5A||EAH/ALR||56 g/l||no||2/3|
*data comparison not applied to these samples (MW6)
There is no threshold dose below which arsenic exposure is known to have no effect. However, arsenic is an element and, therefore, it is found throughout the environment. MDH has not developed a HRL for arsenic at this time, but we are concerned about the possibility of health effects from lifetime consumption of groundwater containing above 2 g/l. When there is no HRL, public water supplies are regulated by the federal MCL which may not be protective of human health. The EPA is mandated to revise the current arsenic standard (50 g/l), and MCLs between 2 and 20 g/l have been discussed. The concentrations listed in the above table, if they were found in drinking water would concern MDH, however, these samples were taken from monitoring wells. Furthermore, MDH believes that at least some of these data appear to be flawed.
The highest reported concentrations (Wenck 1997b), 2 filtered samples with 1000 and 2000 g/l, were from 1983 and were analyzed by a laboratory (SERCO) which had previously reported very high detection limits of 500 g/l. Furthermore, both samples were collected from monitoring wells on the same day, July 11, 1983. Detection limits below 500 g/l were not reported for any of the samples analyzed by SERCO. It is probable that the detected concentrations reported were in error, however the source of the error is not apparent. SERCO has not been used as an analytical laboratory for Windom samples since October 1983. Of the ten samples from MW2 which were analyzed with detection limits below 5 g/l, arsenic was detected in only 1 sample (6 g/l). Similarly one out of four samples from MW3 contained arsenic (1 g/l). The median arsenic concentrations from MW2 and MW3 since 1982 were less than 5 g/l.
The data suggesting 56 g/l arsenic in MW5A was from an unfiltered sample while filtered samples taken less than 2 months later and again in July 1988 from the same well showed no detection of arsenic at 5 g/l detection limit. These were the only samples analyzed from MW5A. The June 22, 1987 sample from MW7A was also an unfiltered sample.
MDH typically analyzes unfiltered supply well samples because water from supply wells represent actual potential exposures of individuals. On the other hand samples from monitoring wells, which are not developed for use and often contain more particulates than drinking wells, are typically filtered (0.2 m).
While not all samples taken from MW6 were filtered, there is reason to believe that groundwater at this well is somewhat contaminated with arsenic. MW6 was constructed as a monitoring well, and is located in the center of the landfill. Landfills can provide reducing conditions in groundwater which could help increase the solubility of arsenic in the landfill or from natural sources. According to data available to MDH, this well was last sampled for arsenic in 1988.
Low level arsenic contamination has been consistently detected at concentrations from 5 to 8 g/l in samples from RWB from 1993 to 1997. A few isolated detections below 10 g/l have also been recorded from MW2, MW7A, and MW7B.
MDH is unaware of any detection of arsenic in City supply wells. However, MDH recommends regular testing for arsenic contamination in the Windom city and monitoring wells as well as periodic testing of local residential wells given:
- the geographic region,
- the history of MW6,
- the proximity of some wells in the Windom area to potential reducing conditions, and
- the anticipated increased municipal pumping on the unconfined aquifer.
Windom Public Water Supply Data
In reviewing Public Water Supply data available to MDH it was noted that there have been low level detections of p-nitrophenol and dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA) metabolites in some samples designated TPE (Well 8) and TPE (Wells 6 and 3) (MDH 1998). It is unlikely that these compounds are associated with the Site. There are no drinking water standards for p-nitrophenol, DCPA, or DCPA metabolites. Toxicity data on p-nitrophenol, DCPA and its metabolites is limited, however, exposure to these compounds at the levels detected is not known to be associated with any health risk.
The source of DCPA is likely non-point and a result of DCPA's extensive use as a pre-emergence herbicide. The contaminant p-nitrophenol is commonly used as a leather fungicide or the compound can also be found in waste material from a coal gas plant (ATSDR 1992). MDH does not have any indication that there has been either a rendering plant or a coal gas plant in the Windom area.
Detection of p-nitrophenol and DCPA metabolites does highlight potential problems with the City of Windom water supply. The presence of these 2 contaminants in city wells demonstrates that water falling as rain may quickly become source water for the city of Windom and the wells may be highly susceptible to contamination.
Since the aquifer which supplies the City of Windom is unconfined, and the city wells are relatively shallow (74 to 124 feet), MDH recommends that the source of the p-nitrophenol be investigated and identified, and that testing for DCPA and metabolites, as well as p-nitrophenol be conducted on samples from the municipal wells on a regular basis. This may be especially important over the next few years, as the demand on the municipal system increases.
Special Issue: Children's Health
In accordance with the Agency for Toxic Substances and Disease Registry's Children's Health Initiative and MDH policy, we are concerned about toxic exposures which may affect children differently than adults and, as a result, may not be addressed in a typical health assessment. This Health Consultation discusses questions about the potential contamination of the City of Windom water system which could affect all residents of Windom. However, children may be exposed to a proportionally greater amount of any contamination due to their typically higher respiratory rate, and their greater surface area to weight ratio. Both of these characteristics increase their need for and ingestion of water, and create a greater absorption potential for children during a respiratory or dermal exposure. Furthermore, it is believed that children, given the development and growth of their bodies, are often more susceptible to chemical toxicity, including the potential development of cancer following exposure to cancer causing agents.
Health risk assessments have been developed by the EPA, MDH, and other governmental entities to determine realistic health-based exposure limits which can be expected to protect the population, including the most sensitive individuals. Children are often defined as the most sensitive individuals. The HRLs, developed by MDH, set limits on the concentration of certain contaminants which should not be exceeded in potable water. These limits are intended to be protective of the health of children exposed to concentrations up to the HRL.
Historically, the chemicals of concern in Windom groundwater have been vinyl chloride, arsenic, and nitrates.
- Vinyl chloride is a health concern due to its cancer causing potential. The HRL for vinyl chloride was developed to protect sensitive individuals, and as such, should be protective of children. It is the understanding of MDH that a specific health risk assessment for vinyl chloride in children is being developed by EPA; however, it is unavailable and has not been reviewed by MDH.
- EPA is developing a new MCL for arsenic which should be health risk based. MDH consistently reviews new research and risk assessments to enable us to maintain standards which are protective of the most sensitive individuals in the population. Special consideration is given to reviewing and appraising health affects on children.
- The HRL for nitrates was developed for a sensitive population: specifically, infants who may be at risk for developing methemoglobinemia. Nitrate levels in drinking water at or below the HRL should be protective of children.